When making round trips with pipes and rods using their vertical stacking in rigs for drilling and servicing wells, it is necessary to readjust said rigs to suit the length of pipes and rods run into the well according to the National Standard of each particular country. That is why to ensure that round trips are made properly, derrickmen have to see to it that the working platform of the rig is positioned according to the length of pipes and rods at an appropriate level above the rig floor. Besides, while replacing rejected drill pipe stands with new ones, they have to be brought from the vertical to horizontal position and then back, which involves changes of appropriate tools and results in lost production time. Thus, cutting down nonproductive time is the main prerequisite for higher efficiency of pipe and rod trips.
There is known a device for handling and stacking drill pipes (SU, A, 256,685), which comprises a grip with slips and toothed blocks positioned in a housing with provision for moving vertically along the guides by means of a lifting mechanism. The grip housing is fitted to a boom which travels horizontally by dint of two bogies, each of said bogies being provided with an electric motor and a control system. The grip housing is provided with a follow mechanism, a lock, and a wedge-shaped head-piece to ensure that a drill pipe is adequately gripped.
Such a construction allows handling and stacking of pipes only in stationary derricks. It cannot be used in mobile rigs for drilling and servicing wells inasmuch as it is pretty bulky, thus making impossible quick readjustment and rigging-up. Practical application of the heretofore-known technical solution considerably decreases operating efficiency of rigs and fails to comply with the requirement for mobility of mobile rigs due to their poor transportability.
There is known a device for gripping and suspending drill pipe stands (SU,A, 15,679), comprising clamping elements which are essentially two clips hinged to each other with toothed blocks rigidly fixed therein. The two blocks are hinged to control levers operated by a handle. The outer surfaces of the clips are provided with eyes to accommodate flexible pull members which are connected with a hoisting line.
This device makes it possible to grip a pipe or rod body in any portion thereof and to move it relative to the well axis. However, to grip a pipe where it is required, the clamping elements are brought to the upper end of the pipe, then the pipe is placed into the opening between the clips, and the device lowered to reach the portion of the pipe to be gripped. Since it is impossible to take hold of the pipe from the side, some additional operations are required when gripping and releasing it, which cuts down production time.
What is more, the known devices employ toothed blocks to grip a pipe or a rod which leave dents on its body.